How to Calculate Solar Cell Efficiency

By Bissan Rafe
Smaller solar cells are more efficient for collecting energy on a smaller scale.
solar cells image by Albert Lozano from

Harvesting the sunlight for energy has been a growing method and a renewed natural alternative to other energy sources. Solar cells are devices that convert sunlight energy into electricity using the photovoltaic effect. The efficiency of a solar cell is a measurement of the amount of sunlight converted into electricity using a particular solar cell module. Higher efficiency means higher electricity production. The efficiency can be calculated from the measurement of four parameters: quantum efficiency, thermodynamic efficiency, fill factor and Voc ratio; therefore, if the area of the cell and the wattage are known, the efficiency can be derived.


Step 1

Determine the area of the solar cell in meter squared (m Sq). For example, if the dimensions of one solar cell is 200 mm Sq x 200 mm Sq, then the cell area is 40,000 mm Sq. Converting mm Sq to M Sq: 40,000 mm sq x .00001 = 0.40 m Sq.

Step 2

Divide the wattage (W) of the solar cell by the cell area to get the efficiency percentile. For example, if the wattage of the given solar cell is 5 Wp (price per Watt Peak), then 5 Wp / 0.40 m Sq = 2% efficiency.

Step 3

Round the answer to three significant digits. For example, 2% efficiency rounded into three significant digits will yield 2.00% efficiency.

About the Author

Bissan Rafe is a Texas-based writer and fine artist who has been writing for over four years. She worked as a cartoonist and columnist for "The Daily Cougar" and as a staff writer for "The Dateline-Downtown." She has published one novel titled "de Clerambault." Rafe is a biology major studying general medicine.